Physics Energy and Friction

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Laboratory: ENERGY AND FRICTION Goals: Show how energy is conserved -- potential and kinetic energy always

add up to the same total energy of the system.

Requirements: Please read the section(s) in your text concerning conservation of energy.

Background: Energy is an abstract concept and difficult to explain in one particular state. It is more convenient to describe energy as it behaves -- how it transforms. We can better understand the processes and changes that occur in nature if we analyze them in terms of transformations of energy from one form into another or of transfers from one place to another. In this laboratory exercise, we study the transformations of potential and kinetic energy. From this we can understand the principles of other energy transformations, for example, mechanical to electrical.

The study of various forms of energy and their transformations from one form into another has led to one of the greatest generalizations in physics -- the law of conservation of energy.

Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes.

Click here to bring up the lab in another window If the above link does not work, please copy the following URL into a browser: https://phet.colorado.edu/sims/html/energy-skate-park-basics/latest/energy-skate-park-basics_en.html

Please become familiar with the components of the lab -- that is, play with the buttons to see how it works....

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Exercises:

1. Setup: Click on Friction (middle button at the bottom) and ensure all indicators are checked:

a. Pie Chart b. Bar Graph c. Grid d. Speed

e. Set the Friction to "None" f. Click Pause and put the person at the very top of the cure on the right

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2. Click Play button. a. What do you notice between the Kinetic and Potential energies as the

person skates along the path?

3. Using the slow motion controls a. At what height is the potential energy equal to the kinetic energy? b. What is the speed (meters/second) of the skater when the kinetic energy

equals the potential energy? c. What is the speed of the skater when the skater is at the bottom of the

curve? d. What is the potential energy when the skater is at the bottom of the curve? e. When the skater is at the bottom of the curve, what does the kinetic

energy equal to?

4. Click on Pause (so the person is at the upper right) and click Restart Skater and set the Friction to Lots. You should see this:

a. At this point, as seen above, what is the kinetic energy? b. At this point, as seen above, what two energies are equal?

5. Click Play

a. As the person goes back and forth, the person loses both what type of energies?

b. The energies in (a) above are converted to what type of energy? c. What causes the energies in (a) to be converted to thermal energy? d. When the person comes to rest, the thermal energy is equal to what

energy? Explain?